Internal combustion engine



Aug. 24, 1937. w. HOWALD v INTERNAL COMBUSTION ENGINE 4 Sheets-Sheet 1 Filed May 9, 1936 lllllt Aug. 24, 1937. w. HowALD INTERNAL COMBUSTION ENGINE Filed May-9, 1936 4 Sheets-Sheet 2 A m m 7 A7 A m m a w 0 0 Aug. 24, 1937. w. HOWALD INTERNAL COMBUSTION ENGINE Filed May 9, 1936 4 Sheets-Sheet 3 Aug. 24, 1937. w. HOWALD INTERNAL COMBUSTION ENGINE Filed May 9, 1936 4 M1 1% m: M w aw I l I t m .t M a l I M u m m U) Ir v l. W m mm SEQ W .n a. 4 m fl 111 m m 0 .M W m .M 2h v b 1* I T v H II I w. I um TN a fi I 0 m k a 8 I a I I r m I n M .w 7 k m m k Patented Aug. 24, 1937 UNlTED STATES PATENT OFFICE Application May 9, 1936, Serial No. 78,874

In Germany May 16, 1935 '7 Claims.

This invention relates to improvements in internal combustion engines, and more specifie cally relates to a working cylinder of such an engine wherein the valves are constituted by a sleeve or sleeves coaxial with the cylinder. The construction of the engine is such that there is provided an outer mantle being in direct connection with the cooling agent, and having near the upper and lower dead centre positions of the 1:; piston movement within inlet and outlet ports. Within this mantle is disposed a sleeve valve sliding up and down, or sliding up and down and oscillating at the same time.

With engines subjected to a high thermic wear,

is for instance with two-cycle Diesel engines of 50 to 100 H. P. per cylinder, the main difficulty is to transmit to the cooling agent the heat imparted to the sleeve valve, and furthermore tomaintain a thin but uninterrupted oil film between sleeve and mantle also, when the engine is running at a high speed and has attained a high temperature. With this film it is possible to reduce friction, wear, and also to prevent a seizing of the sleeve in the mantle. Although a 25 film is strictly necessary, on the other hand only a minimum of lubricant from the crank case should enter the inlet and outlet ports. A third diiilculty with engines of the kind above referred to, consists in ensuring a perfect tighten- 30 ing of the sleeve and mantle etc.

One object of this invention, is to provide means which ensure a perfect transmitting of the heat from the sleeve to the mantle in any case, also when the engine is running at full 55 speed, the said means allowing the formation of an oil film between the sleeve and the mantle.

Another object of the invention, is to give the sleeve and the mantle such a form which, by itself ensures a perfect tightening between in sleeve and mantle. An essential condition for J this perfect tightening, is that the sleeve fits snugly into the mantle, and this at any speed of the engine. Only by such a perfect fitting, the formation of an uninterrupted oil film is made possible, and only this oil film allows the heat of the sleeve to be transmitted to the mantle. The film is also necessary for obtaining a perfect tightening of the sleeve in the mantle.

50 Another purpose of the invention, is to adjust the clearance between sleeve and mantle along their whole length in such a way, that in any position of the piston and under any thermic condition of the engine not only the transmis- 55 sion of the heat and the tightening is a maximum, but that also a jamming of the sleeve is accurately prevented.

A further purpose of the invention is to provide for an automaic adjustment of the heat flow from the sleeve valve to the mantle. When 5 setting the motor in motion this flow'is produced automatically. Care must only be taken that by the motion of the sleeve on-the one hand, and by the difference'in temperature (along an axial section through the working cylinder) on the other hand, this heat flow is not disturbed when the load of the engine is altered. This means that the resistance to the heat transmission should not increase locally, but on the contrary the said resistance should decrease, and become a minimum when the engine is working under full load. For this purpose it is essential to determine the exact temperature along a. line out out from the sleeve and the mantle by an'axial section through the working cylinder. These temperatures have to be measured when the engine is working under full load, when the resistance to the heat transmission and the sliding resistance of the sleeve is a minimum. These two conditions are fulfilled when an oil film is formed between the two surfaces of sleeve and mantle moving one with respect to the other.

The main purpose of the invention consists in the fact of giving, after having exactly determined the temperatures along a meridian of the mantle and the sleeve, the latter such a form that their gliding surfaces are exactly or at least practically cylindrical when the engine is working under full load and when it has attained the working temperature, and that an extremely small oil film with parallel flow is formed between sleeve and mantle.

Having set forth generally the improvements to be attained in order to secure the beforementioned objects, the means employed toward accomplishing such end will now be described and illustrated by the accompanying sheets of drawings. Of the drawings:

Fig. 1 is a vertical section through a portion of the cylinder in a diagrammatic view, the exhaust being located at the upper end of the cylinder.

Fig. 2 is a veritcal section through the same cylinder after it has become heated during operationf The temperatures prevailing then are shown and the deformations are illustrated in an exaggerated way. I

Fig. 3 is a vertical section through another embodiment of the cylinder in cold condition. 5

The exhaust is located at the lower end of the cylinder.

Fig. 4 is a diagrammatic View of these parts in heated condition.

5 Fig. 5 is a section through the upper portion of a cylinder in which the top of the sleeve valve is cylindrical and very thin.

Fig. 6 shows an embodiment of a sleeve tapering upward.

10 Fig. 7 is another modification in which the the sleeve is reinforced at its upper end.

Fig. 8 is a diagrammatic axial section of an embodiment wherein the sleeve engages the wall of the cylinder under tension.

15 Fig. 8a. shows the position of the sleeve 3 with respect to the mantle I in Fig. 8 above.

Figs. 9, 9a, and 10-10a, show, in a manner similar to Figs. 8, 8a., another embodiment of the sleeve.

Figs. 11, 110. show in asimilar manner a sleeve provided at its upper'end with a collar or other reinforcement.

' Reference number I refers to the mantle surrounding sleeve 3. Said mantle is fixed in the cylinder block and" can be cooled by a cooling agent. It is provided with ports a. and b, communicating with exhaust-and scavenging channels not shown in the drawings. The cylinder cover 2 is fixedly connected to the mantle I, and

.3 projects into the upper end of the sleeve. Cover 2 may be provided with a packing ring section e with the packing ring 0'. In sleeve 3 which moves up and down, is located piston 4 with ring section 0, rings 0', oil retaining ring 0" and skirt 35 d. The inlet and outlet channels and the slits a. are disposed regularly on the whole circumference of the mantle and the sleeve. The Figures 1 to 11 show sleeve 3 in its upper dead center. The dotted lines 3' indicate the lower dead centre posi- 40 tion of the sleeve. According to the modification shown in Figs. 1 and 2, the exhaust of the combustion gases takes place at the upper end of the cylinder, while the inlet for scavenging-air and fresh mixture is at the lower end of the cylinder.

45 The Figures 3 and 4 show a part of working cylinder with cylinder cover and piston in a schematical manner. Fig. 3 shows these parts when the engine is still cold, and Fig. 4 shows the form of them when the engine is warm. But in E0 the modification according to these Figures 3 and 4, the exhaust takes place at the lower cylinder end while the inlet for the mixture and of the scavenging air is at the upper cylinder end.

The Figures 1 to 4 show on a very large scale c the form the bore'of mantle I and the size the inner and outer diameters of the sleeve along a meridian have to be given when being cold, in order to have all three gliding surfaces exactly cylindrical when the engine is working under full load. The drawings refer to a water cooled engine working according to the two-cycle principle, with an output of 100 H. P. per cylinder, and 12 meters per second mean piston speed.

It can be seen from the Figures 1 and 2 that 6, the temperature of mantle I above and below the exhaust channels (the exhaust takingplace at the upper cylinder end), is about 140 centigrade Whereas it amounts at the lower cylinder end, where the scavenging air and the fresh mixture enter the cylinder, only to 60 centigrade.

If the bore of mantle I is 164 mm. and the mantle isto be exactly cylindrical at the working temperature the diameter of the mantle should decrease by about "0.19 mm. per 10 mm. towards the "upper end. Also the sleeve, the temperature of which is 70 centigrade at the lower and 160 at its upper end, should therefore have a taper of 0.19 mm. per 10 mm. when cold if it is to be completely cylindrical at working temperature. When determining the exact deformations 5 the stresses caused by the temperature in the sleeve and in the mantle have to be taken into account.

If in such highly stressed engines sleeve and mantle were made exactly cylindrical when be 10 ing cold, these parts would become trumpetshaped when becoming warm. If such a trumpet-shaped sleeve has to move in the mantle, the clearance near the upper dead centre between sleeve and mantle must be at least several A 15 mm., whereas on the contrary near the lower dead centre there is no clearance at all or even an overmeasure. This alternating clearance has the drawback that no laminarly moving oil film can be formed between sleeve and mantle, but 0 only an oil foam is produced which finally is ejected through the exhaustand the scavenging channels.

For air cooled engines or for engines cooled with vapor or ethylene glycol, the cooling medium temperature of which is about 120 to 140 centigrade, the invention is still more important than for highly stressed water-cooled engines.

If the exhaust takes place at the upper cylinder end, the cylinder mantle has near the exhaust channels a temperature of about 230 centigrade, Whereas the temperature of the sleeve in that region may rise to 260 centigrade. The temperatures' of the sleeve and of the mantle at the lower end of the working cylinder, may at the same time vary between 100 and 150 centigrade, and the temperatures of the lowest parts of the sleeve and mantle depending into the crank case, vary between 70 and 120 centigrade.

By arranging the inlet for the scavenging-and 40 the charging air and the inlet of the fresh mixture at the upper cylinder end, and the exhaust of the hot combustion gases at the lower end of the cylinder, the upper end of the cylinder which is a priori the hotter part of mantle and sleeve, can effectively be cooled down by the scavenging-or charging air, or by the fresh mixture. The lower end of the sleeve on the contrary, is heated by the hot combustion gases leaving the cylinder there. The Figures 3 and 4 show such a working cylinder in a schematical manner, together with the approximate temperatures occurring when the cylinder is provided with the usual water cooling.

As can be seen from the Figures 1 to 4, the lower end of the mantle depending into the crank case may be made exactly cylindrical, if the exhaust channels are disposed at the upper end of the cylinder. But if theexhaust channels are arranged at the lower end of the cylinder, these lower parts of themantle have to be made partially conical, if the clearance between mantle and sleeve is to be constant during an entire stroke of the sleeve. This clearance must be constant also when the engine has attained working temperature, and should not be above 3 mm. if an un- 05 interrupted parallel flow of the oil film is to be formed.

When the engine is cool and when it is set in motion, these conditions are never fulfilled. But this just impedes a ready transmission of heat "0 from the sleeve to the mantle. The sleeve thereby gets warmer and expands. The clearance between sleeve and mantle thereby becomes gradually smaller, and accordingly the resistance to the passage of heat becomes also smaller. Then flow of heat from the sleeve to the mantle, increases always until finally a certain position of equilibrium is arrived at, in which the heat imparted to the sleeve, is equal to the heat transmitted by the sleeve to the mantle. Such a position of equilibrium occurs always, independent of whether the engine is working under full load or not. Only the flow of heat is naturally greater when the engine is working under full load, than when it works only with half load for instance. If the initial clearance between sleeve and mantle on the one hand, and the form of the initial meridian on the other hand is chosen adequately, there results not only a perfect cooling of the engine, but at the same time this invention ensures an accurate packing of the working chamber by the mantle and the sleeve. Any danger of seizing or clamping is completely obviated.

It is quite clear that it is advantageous to make the sleeve of a material with minimal thermic expansion. Moreover the wall of the sleeve should be very thin compared with diameter of the sleeve.

Such a thin-walled sleeve has the advantage that, when employed in cylinders with high compression and high mean speed of the piston, it is pressed uniformly on the surrounding mantle by the exploding combustion gases, if only the clearance between mantle and sleeve is chosen adequately. Another advantage of this form of construction, is that the stress due to the action of the mass is a minimum. Because the sleeve is to a certain extent elastic, it ensures just in the deciding moment, a perfect tightening between sleeve and mantle. And because in this moment the sleeve is pressed on the mantle, the transmission of heat from the sleeve to the mantle is in this moment, where a maximum of heat is produced also a maximum.

In engines designed according to the principles of this invention, and in which the coefiicient of thermic expansion of the mantle material is equal to or only slightly greater than that of the sleeve material throughout all occurring temperatures, and in which engines these materials possess the highest possible running qualities, the usual packing rings which often occasion interruptions in the working of the engines, can completely be dispensed with. This because the main purpose of these rings is to allow an easy start of the en gine when the latter is still cool, and when therefore the sleeve does not perfectly tighten the working chamber. One condition for doing away with the packing rings, is firstly that the surface of the sleeve cooperating with a part of the mantle surface outwardly of the inlet or outlet slits, is elastically pressed on the said part of the mantle surface, and secondly that these overlapping surfaces which are employed for opening and closing the working chamber are as short as possible, preferably shorter than one third of a stroke of the working piston.

The modifications of the guiding and closing parts of the sleeve valve according to the Figs. 5 to 11, completely fulfill all these requirements.

In engines in which the scavenging and charging air enters at the upper end of the cylinder, the free and overlapping end of the sleeve is preferably made cylindrical but very thin walled, or it may be made conical on its inner wall so that at the top the edge has just the thickness that is strictly necessary. This guiding edge or the thin walled cylindrical upper part of the sleeve, is resiliently pressed against the inner wall of the mantle as soon as a small over-pressure occurs in the working cylinder. Thereby an easy running is ensured when the cold engine is started and moreover a perfect tightening is attained, irrespective of the load and of the working temperature. In this case a clearance between 0 to 0.005 mm. is quite sufficient. The Figs. 5 and 6, show two modifications of the upper edge of the sleeve as above described in the upper dead centre of the sleeve. The dotted lines show the upper guiding edge of the sleeve'in the lower dead centre of the latter. The dot and dash lines mark another modification of the tightening surface of the sleeve, and of the cooperating surface of the mantle.

A complete tightening of the working chamber by the resilient upper edge of the sleeve, is preferably arrived at even when the engine is cold and when there is no interior overpressure, by giving the overlapping part of the sleeve when the overlapping is a maximum at its root, that is in front of the upper steering edge of the ports in the mantle, an undermeasure (clearance) of 0 to some mm. By gradually and conically flaring the overlapping part of the sleeve until to its upper guiding edge in front of the fixed steering edge of the mantle, this undermeasure of 0 to some becomes an overmeasure (surplus measure) of some. mm. In many cases it will be advantageous to give an overmeasure to the entire outer half, or to the most outward third or fourth part of the overlapping part of the sleeve, or to give such overmeasure to the innermost part of the mantle containing the guiding edge. The Figures 8 to 11, show such sleeves in their upper dead centre. The cylinder covers and working pistons employed in these cases, are identical to those shown in the Figs. 5 to '7.

The Figures 8a to 11a drawn below the Figures 8 to 11, show the form which the upper ends of the sleeves according to the Figs. 8 to 11 take, when being taken out of the mantle i. It is obvious that the tightening surfaces have resiliently moved radially outwardly by the distance M between the two thin. lines of the drawings. This distance M represents the maximum overmeasure. When the sleeve is placed in the mantle the free end of the sleeve is along its entire circumference moved radially inwardly (and thereby given the form of a cylinder) by the distance M, and thereby ensures a perfect tightening also when the engine is cold, and when there is no overpressure in the working cylinder. Also an easy running is always possible, as the designer can make the upper edge of the sleeve more or J less thick, and the amount of overmeasure more or less great in the various parts of the sleeve or of the mantle, so that an oil film between sleeve and mantle can never be destroyed or torn. The ports are preferably disposed in great number and are made very small, so as to prevent the thin and resilient edge of the sleeve from projecting into the ports. But the ports might also be substituted by .a great number of nozzlelike holes arranged beside and above each other.

In engines in which the exhaust is controlled by the free end of the sleeve, or in which the width of the slits is great as compared with their height, it may be advantageous to give the free end of the sleeve the form shown in Figs. '7 and 11. In this case the wall just below the edge is made thinner than the edge itself. The latter is further preferably given a little undermeasure of 0 to some mm. In this case the end of the sleeve forms a collar 5, the thickness of which corresponds approximately to its height. This collar also stiifens the sleeve, and prevents the latter from being too much heated or even burnt by the exhaust gases, as would be the case if the upper edge of the sleeve were made as thin as shown for instance in Fig. 10. If the upper edge were made too thin, the oil film would be burnt at least partially. The collar in conjunction with the undermeasure, prevents the upper edge from projecting into the slits of the mantle over which the sleeve is gliding.

Instead of making the upper overlapping free end of the sleeve thinner towards its upper edge, it might on the contrary also be made thicker (Fig. 8).

By alternating the form of the upper end of the sleeve, any desired pressure can be exerted on the mantle. By letting the thickness of the sleeve gradually increase towards its upper edge, it is possible to exercise an equal pression on the mantle when the highest pressions occur in the Working chamber; but such constructions necessitate highest precision in manufacture of sleeve and mantle, because the sleeve attains a high degree of stiffness.

It is preferable not to change the thickness of the sleeve or the form. of the mantle too abruptly, but to alter the same gradually, for instance by interposing conical parts between the parts of different diameter. In the Figures to 11, several forms of such intermediate parts K are shown.

In order to keep the volume of the oil film enclosed between mantle and sleeve constant, the

" packing rings should be so arranged with respect to the outer surface of the sleeve and of the inner surface of the mantle, as to keep the volume of the enclosed oil film constant also when the sleeve is moving.

An essential characteristic of the invention therefore lies in the fact that after the start of the engine, at once an oil film is formed between the mantle and the sleeve, which film never tears no matter what the load on the engine be, be cause of the constancy and the minimal size of the clearance. On the contrary the oil forms a highly viscous film, which is in contact with both the sleeve and the mantle wall. By this contact and by the parallel flow of the oil film, the same transmits the heat at once from the sleeve to the cooled mantle. Further it ensures a perfectly easy running of the sleeve in the mantle, and finally a perfect tightening of the working chamber by sleeve and mantle themselves when the engine is cold and when it is warm.

When in the claims I refer to the sleeve valve as being movable along the axis of the cylinder or movable on the running surface of the said mantle I desire those terms to include either a simple reciprocating movement or a combined reciprocating and turning (or oscillating) movement.

Having now described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:-

1. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof so that the inner sliding surface of said mantle and the outer sliding surface of said sleeve valve assume substantially the shape of concentric cylinders when the engine is working under full load.

2. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof, the outer running surface of said sleeve valve having its smallest diameter in the neighborhood of the ports near the hotter end of the working chamber and from this point both the inner sliding surface of said mantle and the outer sliding surface of said sleeve valve being gradually enlarged along a certain distance towards the cooler end of the working chamber while at the crank case end both said sleeve valve and said mantle are of cylindrical shape.

3. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said'sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof, the said sleeve valve having a cylindrical outer running surface at its overlapping end in the neighborhood of the hotter end of the working chamber.

4. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof, the outer running surface of said sleeve valve and the inner running surface of said mantle having no clearance between them in the zone of the overlapping tightening surfaces.

5. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantle-d condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof, said mantle having ports, a control edge and tightening surface at the said ports, an overlapping outer end of said sleeve valve overlapping the said ports and the said control edge and tightening surface, the outer guiding and tightening free end of said sleeve valve having an overmeasure with respect to the tightening surface of said mantle, the inner wall of the overlapping free end of the said sleeve valve being thin walled and provided at its outer end with a collar.

6. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood of the hotter end of said working chamber than at the cooler end thereof, said mantle having ports, a control edge and tightening surface at the said ports, an overlapping outer end of said sleeve valve overlapping the said ports and the said control edge and tightening surface, the outer guiding ring and tightening free end of said sleeve valve having an overmeasure increasing gradually towards the outer end of the said sleeve Valve and being of such size that, when pressed together by the said mantle, the said free end of the sleeve valve becomes cylindrical and bears cylindrically against the said mantle running surface.

'7. In an internal combustion engine a cylinder, a piston, an outer mantle having an inner running surface; a sleeve valve movable on said running surface and itself provided with an inner and an outer running surface, said piston being adapted to run on the inner running surface of said sleeve valve, said mantle, said sleeve valve and said piston forming a working chamber with ports near the dead center positions of said piston, the diameters of said inner running surface of said mantle and of said outer running surface of said sleeve valve being in cold and dismantled condition smaller in the neighborhood'of the hotter end of said working chamber than at the cooler end thereof, said mantle having ports, a control edge and tightening surface, a control valve overlapping the said ports and the said control edge and tightening surface, the outer guiding and tightening free end of the sleeve valve having an overmeasure with respect to the said tightening surface, the maximum overmeasure being within the first two thirds of the overlapping free end of the said sleeve valve and from there decreasing again.

WERNER HOWALD. 

